Locks are the key to a successful policy claim

Worryingly, the majority of householders have no idea of the precise type of locks that are fitted to any of their doors, yet blithely believe that the existing locks would meet safety standards, insurance brokers have warned.

But these householders could find themselves thousands of pounds out of pocket if their home is burgled and they try to make an insurance claim.

If the insurer believes the locks don't measure up to standards, it could lead to a claim on your policy being deemed as invalid.

"The problem with claims over locks is down to ignorance," warns Peter Staddon, head of technical services at the British Insurance Brokers' Association (Biba): "To discover your lock type, half the time you have to physically take the lock out of the door: a messy job you really don't want."

Too many homeowners slog through price comparison websites and weigh up dozens of rival insurers to lop hundreds of pounds off their home insurance policy, but breeze through final vital questions such as: "are the locks British 'safety-standard', a five-lever mortice lock conforming to BS3621, or a cylinder rim deadlock?"

If you've drawn a blank at the gobbledegook, you're in good company. For most home contents policies, the phrase runs: "You must have a 'five-lever mortice lock' conforming to BS3621 on all exit doors and key-operated locks on all ground floor and accessible windows" - although the wording may vary slightly. Not all policies insist on such locks, however, some offer you a discount of up to 5% if you have them installed.

But unless you've recently moved into a new-build home where it's made clear that the developer has specifically fitted such locks, it's difficult to tell which locks you have without the benefit of specialist knowledge, says a spokesman for the Financial Ombudsman Service (FOS).

If you are unsure of which locks you have at home, you can always tick "no" on the forms, but you may end up paying a substantially higher premium on your policy.

To ensure you don't leave yourself exposed to problems with any future claim ask your insurer if they would send you - by post or email - a diagram clearly showing the different types of locks. You can also find a clear depiction of different lock types at sterlinginsurancegroup.com on its home security page.

The FOS also warns that insurers often refuse to pay out if burglars break in through a bathroom window that has been left ajar, regardless of whether you have the correct locks. The FOS sees scores of complaints about the issue, and upholds the majority in favour of the consumer.